Testing circuit



July 8, 1941. LANE IESTING cmcun' Filed June 15, 1940 Mp. map

ATTORNEY Patented July 8, 1941 TE STING CIRCUIT Leland Gifford Lane,Trinidad, Colo assignor to American Telephone and Telegraph Company, acorporation of New York Application June 15, 1940, Serial No. 340,797

8 Claims.

This invention relates to arrangements to test for faults ontransmission lines, and particularly to arrangements to test for faultsof a temporary or recurrent nature.

Apparatus is well-known in the telephone art capable of testing forfaults of a continuous or more or less permanent character, such aspermanent grounds, continuously crossed lines or short-circuits, etc.There is, however, a type of fault which is frequently met with, whichis not continuous but recurs at infrequent intervals. A common fault ofthis kind is the condition resulting from so-called swings. Under theseconditions the two wires forming a line sway back and forth with thewind with the result that the two wires occasionally come into contactwith each other. This produces a so-called hit resulting from atemporary cross or short-circuit which lasts only a brief interval, andmay not recur again for many minutes or even for hours.

A bit may also result from one side of a line swing into contact with aWire of an adjacent line. An alternative condition is that existing whenone of the wires in swinging makes contact with a grounded element. Hereagain the condition, while quite deleterious to proper telephoneservice, may exist only for a brief period and may not recur again untila considerable interval has elapsed.

While existing testing equipment would be capable of locating suchfaults, if it were possible to watch the indicating instrumentscontinuously, this would necessarily detach employees at all repeaterstations from their regular duties to make the necessary observationsover a consider- 0 able period of time. Moreover, the making of suchobservations is considerably handicapped by the fact that in arepeatered telephone line it is diflicult to determine during the briefexistence of a hit just what repeatered section is involved.

The present invention makes available a simple and cheap apparatus whichmay be used to detect and locate the repeater section in which suchfaults occur without necessitating the continuous supervision orobservation of an attendant. This may be accomplished by providing atesting circuit capable of giving a continuous indication as the resultof a temporary fault such as a hit.

The invention will be now more fully understood from the followingdescription when read in connection with the accompanying drawing, thefigure of which shows the invention as applied to an ordinary repeateredtelephone line which is composited for transmission of superposedtelegraph signals,

Referring to the drawing, a telephone transmission line L is shownextending through two repeater stations A and B at which telephonerepeaters of the usual type are provided at Re. and Rb. The linesections coming into either side of a repeater are connected on the twosides of the repeater to composite sets, as shown at CSa, CS'a, CS1; andCSb. These composite sets are connected to so-called Morse or telegraphlegs such as are shown at TLa, RLa, RL'a, TLa, etc. By means of thesecomposite sets telephone currents may be transmitted over the line Lthrough the repeaters Ra and Rb, but in each line section the telegraphcurrents, which are separately trans mitted over the two sides of theline by means of ground returns, are prevented from entering therepeaters and are diverted into the Morse legs. transmitting thetelegraph currents around the repeater or for transmitting them to localloops or to telegraph lines terminatingat the repeater point.

A circuit arrangement such as abovedescribed, when carried over an openwire line, is subject to so-called swings which may result intemporarily grounding either side of the line, or in shorting togetherthe two sides of the line, or in putting one side of the line in contactwith one of the wires of another line. These effects, while temporary,are recurrent, and render the line unsuitable for telephone andtelegraph purposes while the effect is present.

In order to test for faults of the above character, testing circuits orso-called hit alarm circuits of the present invention are provided asshown at HA and HA1; for application to the line at the repeater pointsA and B, respectively. Of course it will be understood that similar hitalarm circuits will be provided for other repeater points not shown inthe diagram.

The hit alarm circuit HAb, for example, terminates in plugs TPb and RPb,which may be inserted in jacks T11}: and Hit of the telegraph legs TLband RLb, respectively. The plug 'IPb is connected to a relay TBb in thehit alarm circuit which is connected to a telegraph battery,

which in the instance shown supplies a negative voltage of 139 volts.The relay 'IRs is of the locking variety and when operated by a hitlocks up until such time as an attendant may release it by operating keyTKb. One armature of the relay TRb controls the circuit of a relay 'IR'bwhich at its right-hand contact closes the circuit of an indicating lampTLb, and at its The Morse legs may be used either for the transmissionline.

left-hand contact closes the circuit of a buzzer Bb- Similarly the plugRPb leads to a locking relay RR!) and through a release RKb to a plus130 volt battery. The relay RRb in turn controls a relay RRb, which atits left-hand contact controls the circuit of a signal lamp RLb, and atits right-hand contact controls the circuit of the buzzer Bb.

The apparatus HA3. shown at repeater station A'is similar in allrespects to the apparatus HAb just described and, of course, similarapparatus is provided at all of the repeater points.

If it is found that the transmission line is subject to so-called hits,the attendant at each repeater station will apply his hit alarm circuitsto the telegraph legs on one side of the repeater at his station. Forexample, at repeater station B the plugs TPb and RH; will be inserted inthe jacks Tub and RJb of the telegraph legs TL]; and

RLb. At the same time dead plugs will be inserted in the jacks, TJ'b andRJfb on. the other side of the repeater to open the telegraph legsincoming from the east.

So also the plugs TPb and RR of the hit alarm HA2 are inserted in thejacks of the telegraph station B. If there are nogrounds on the sides ofthe line, and if there is no cross or short between the two sides of theline, the circuits from I the plugs TPb ELIId'RPb through the relays TRband RRn are open-circuited because the telegraph legs at the rightofrepeater Ra are open. The result is that no indication will be given onthe hit alarm circuit.

If, however, the upper conductor of the line between repeater stationsA-- and B should be grounded temporarily as aresult of a swing, thusgiving a so-called hit, current will flow over the upper conductorthrough the composite setjjack TJb and plug 'I'Pgthrough the relay TRband the resistances'in'series therewith to the negative 130 voltbattery. 7 Although this hit may be but temporary, the relay 'I'Rb willbe operated and locked up and will in turn operate the relay TR'b tocause the lamp TLb to glow continuously and the buzzer Bb to give forthan audible signal. I

An attendant seeing the lamp or hearing the buzzer will know fromthe-fact the lamp 'ILb is operated "and the lamp R11]: is not operatedthat a hit is arriving from the section between repeater stations A andB over the upper side of Informed of this fact, the attendant may use aWheatstone bridge or other known equipment to determine the approximatepoint in the section at which the fault is located. This will of courseinvolve watch ing the line until a hit'capable of being tested 7occursi; The approximate location being known I ,a repair man willinspect this particular line section to find the cause of the fault. Inthe meantime the attendant will open the key TKb to unlock relay 'I'Rbandrestore the hit alarm apparatus to normal.

' If, on the other hand, the lower conductor of the line should betemporarily grounded as a result of a swing, the relay RR}; will beoper-c 7 legs The and RLB, at the repeater station A and one wire of theline shown in the diagram swinging into contact with a wire of someother linerelays TRb and RRb.

1 not be indicated on the alarm circuit HAb.

'ated, thus actuating the relay RRb to cause the lamp RBI: to glow,thereby informing the attendant that a hit has occurred on the lowerconductor between the line sections A and B. Having ascertained thisfact and having by known means approximately located the fault in thesection, the attendant may restore the hit alarm apparatus to normal byoperating the key RKb. A repair man may then be sent out to remedy thetrouble.

If the swing results in temporarily crossing or shorting together thetwo sides of the line, as indicated by dotted lines between the repeaterstations A and B, a momentary circuit will be.

completed from the positive volt battery, through the resistance andrelay RRb of the alarm circuit, over the plug RPb and the jack RJb,thence through the composite set to the lower conductor of the line tothe point at which the cross occurs. From this point the circuitcontinues over the short circuit connection to the upper line and backthrough the composite set and telegraph leg to jack- TJb and plug TPb,and thence through the relay 11% and the resistance in the alarm circuitto the negative 130 volt battery.

This results in actuating and locking up both The consequence is thatnot only the buzzer Bb is set into operation but both lamps 'ILb and RLbare caused to glow, and this latter fact indicates to the attendant thatthe hit was caused by crossing the two sides of the line or bringingthem into contact with each other between repeaters A and B. Havingascertained this fact, the attendant may restore the alarm circuit byactuating eitherkey TKa or TKb. V

It will be noted that a hit occurring between the two repeater stationsA and B will not afiect" a hit alarm circuit to the east of repeater B,becausethe composite circuit CSuprevents the hit from passing throughits series line condensers to the repeater B. Likewise hits occurring inthe line L to the west of repeater station A willv The currentsresulting from these hits will not pass through the composite sets oneither side of the repeater'Rav and over the intervening line section tothe station E. f

It will be apparent that a hit may resultfrom such as the line L. Inshort a hit occurs when any two wires on the same pole line come intocontact. when it is known that the hit involves two wires of difierentline circuits the hit alarm apparatus may be plugged into the jacks ofthe two'wires involved. when the hit occurs the section in which itoccurs will be indicated upon the hit alarm apparatus in a mannersimilar to a hit involving two wires in the same line. The hit will ofcourse-register only on the hit alarm circuit associated with thesection in which the swing took place. The exact location of the faultmay then be determined by an attendant at the, nearest repeater station,who may use a .Wheat stone bridge or other known equipment for thepurpose. 7 section which is in trouble until a measurable He must ofcourse watch the line hit occurs.

It should be understood in connection wi-thhits that although the directcurrent resulting therefrom will not pass beyond the line section inwhich it occurs, the hit will impair; the usefulness of the line at allpoints along its length for telephone purposes. This is because the linewill be effectively shorted or grounded from an alternating currentstandpoint during the continuance of the hit.

What is claimed is:

1. Telephone lines each including a plurality of repeaters connected byline sections, apparatus to observe faults at each repeater point, saidapparatus including separate indicating devices adapted to be connectedto each of a pair of line wires at the repeater point, said indicatindevices being arranged to give a continuous indication in response to atemporary but recurrent fault in the line section to which the apparatusis connected.

2. Telephone lines each including a plurality of repeaters connected byline sections, apparatus to observe faults at each repeater point, saidapparatus including separate indicating devices adapted to be connectedto each of a pair of line wires at the repeater point, said indicatingdevices being arranged to give a continuous indication in response to atemporary but recurrent fault in the line section to which the apparatusis connected and being unresponsive to faults in other line sections.

3. Telephone lines each including a plurality of repeaters connected byline sections, apparatus to observe faults at each repeater point, saidapparatus including separate indicating devices adapted to be connectedto each of a pair of line wires at the repeater point, said indicatingdevices being arranged to give a continuous indication in response to atemporary but recurrent fault in one wire of the line section to whichthe apparatus is connected.

4. Telephone lines each including a plurality of repeaters connected byline sections, apparatus to observe faults at each repeater point, saidapparatus including separate indicating devices adapted to be connectedto each of a plurality of wires at the repeater point, said indicatingdevices being arranged to give a continuous indication in response to atemporary but recurrent fault involving two wires of the line section towhich the apparatus is connected.

5. Telephone lines each including a plurality of repeaters connected byline sections, telegraph legs connected to each side of each section ofline at each repeater point, apparatus to observe faults at eachrepeater point, said apparatus including separate indicating devices foreach of a plurality of wires at the repeater point, means to connectsaid indicating devices separately to the telegraph legs associated witha plurality of wires of the line section, said indicating devices beingarranged when so connected to give a continuous indication in responseto a temporary but recurrent fault in the line section with which theapparatus is associated.

6. Telephone lines each including a plurality of repeaters connected byline sections, telegraph legs connected to each side of each section ofline at each repeater point, apparatus to observe faults at eachrepeater point, said apparatus including separate indicating devices foreach of a plurality of wires at the repeater point, means to connectsaid indicating devices separately to the telegraph legs associated witha plurality of wires of the line section, said indicating devices beingarranged when so connected to give a continuous indication in responseto a temporary but recurrent fault in the line section with which theapparatus is associated, and being unresponsive to faults in other linesections.

7. Telephone lines each including a plurality of repeaters connected byline sections, telegraph legs connected to each side of each section ofline at each repeater point, apparatus to observe faults at eachrepeater point, said apparatus including separate indicating devices foreach of a plurality of wires at the repeater point, means to connectsaid indicating devices separately to the telegraph legs associated witha plurality of wires of the line section, said indicating devices beingarranged to give a continuous indication in response to a temporary butrecurrent fault in one wire of the line section to which the apparatusis connected.

8. Telephone lines each including a plurality of repeaters connected byline sections, telegraph legs connected to each side of each section ofline at each repeater point, apparatus to observe faults at eachrepeater point, said apparatus including separate indicating devices foreach of a plurality of Wires at the repeater point, means to connectsaid indicating devices separately to the telegraph legs associated witha plurality of wires of the line section, said indicating devices beingarranged to give a continuous indication in response to a temporary butrecurrent fault involving two wires of the line section to which theapparatus is connected.

LELAND GIFFORD LANE.

